Riot police firing tear gas and wielding clubs stormed a landmark square occupied by anti-government protesters before dawn Thursday, driving out demonstrators and destroying a makeshift encampment that had become the hub for demands to bring sweeping political changes to the kingdom.

The main opposition group Al Wefaq said at least two people were killed in the assault on Pearl Square, which was littered with flattened tents, trampled banners and broken glass. There was no official word on deaths or injuries, but hospitals treated dozens of people with serious gaping wounds, broken bones and respiratory problems from the tear gas.

Hours after police retook control of the plaza, the tiny island nation was in lockdown mode. Tanks and armored personnel carriers were seen in some areas — the first sign of military involvement in the crisis. Police checkpoints were set up along main roadways and armed patrols moved through neighborhoods in an apparent attempt to thwart any mass gatherings.

Barbed wire was put up around Pearl Square and a message from the Interior Ministry declared the protest camp "illegal." The air still carried the smell of tear gas more than four hours after the assault.

The blow by authorities marked a dramatic shift in tactics. It appeared Bahrain's leaders had sought to rein in security forces after clashes Monday that left at least two people dead and brought sharp criticism from Western allies — including the U.S. — which operates its main naval base in the Gulf from Bahrain.

Police held back Wednesday as tens of thousands of protesters crowded into the seaside square, dominated by a 300-foot (90-meter) monument to Bahrain's history as a pearl diving center.

After the crackdown early Thursday, protesters who were camped in the square overnight described police swarming in through a cloud of eye-stinging tear gas.

"They attacked our tents, beating us with batons," said Jafar Jafar, 17. "The police were lined up at the bridge overhead. They were shooting tear gas from the bridge."

Many families were separated in the chaos. An Associated Press photographer saw police rounding up lost children and taking them into vehicles.

Hussein Abbas, 22, was awakened by a missed call on his cell phone from his wife, presumably trying to warn him about reports that police were preparing to move in.

"Then all of a sudden the square was filled with tear gas clouds. Our women were screaming. ... What kind of ruler does this to his people? There were women and children with us!"

One man said he pretended to be unconscious to avoid further beatings from police.

ABC News said its correspondent, Miguel Marquez, was caught in the crowd and beaten by men with billy clubs, although he was not badly injured.

The Egypt-inspired protests began Monday as a cry for the country's Sunni monarchy to loosen its grip, including hand-picking most top government posts, and open more opportunities for the country's majority Shiites, who have long complained of being blocked from decision-making roles or key posts in the military.

But the uprising's demands have steadily grown bolder. Many protesters called for the government to provide more jobs and better housing, free all political detainees and abolish a system that offers Bahraini citizenship to Sunnis from around the Middle East as a way to close the population gap with Shiites, who account for 70 percent of the population. Many of the newly minted nationals get jobs in security forces to further cement the number of presumed loyalists protecting the ruling system.

Increasingly, protesters also chanted slogans to wipe away the entire ruling dynasty that has led Bahrain for more than 200 years and is firmly backed by the Sunni sheiks and monarchs across the Gulf.

Although Bahrain is sandwiched between OPEC heavyweights Saudi Arabia and Qatar, it has limited oil resources and depends heavily on its role as a regional financial hub and playground for Saudis, who can drive over a causeway to enjoy Bahrain's Western-style bars, hotels and beaches.

Social networking websites had been abuzz Wednesday with calls to press ahead with the protests. They were matched by insults from presumed government backers who called the demonstrators traitors and agents of Shiite powerhouse Iran. Some pointed out that Iranian hard-liners have called Bahrain the Islamic Republic's "14th province" because of its Shiite links.

The protest movement's next move is unclear, but the island nation has been rocked by street battles as recently as last summer. A wave of arrests of perceived Shiite dissidents touched off weeks of rioting and demonstrations.

Outside the main state medical complex — where many injured protesters were treated — dozens of protesters chanted: "The regime must go."

Before the attack on the square, protesters had called for major rallies after Friday prayers. The reported deaths, however, could become a fresh rallying point. Thousands of mourners had turned out for the funeral processions of two other people killed in the protests earlier in the week.

Mahmoud Mansouri, whose pants were torn in the mayhem, said police surrounded the camp and then quickly moved in.

"We yelled, "We are peaceful! Peaceful! The women and children were attacked just like the rest of us," he said. "They moved in as soon as the media left us. They knew what they're doing."

The country's rulers scheduled an emergency parliament session for later Thursday. But it may only serve to highlight the country's divisions and reinforce its image as the most politically volatile in the Gulf.

The main Shiite opposition bloc, with 18 of the 40 seats, has said it will not return to the chamber until the protest demands are met.

The occupation in Pearl Square, which began Tuesday, had become the nerve center of the first anti-government protests to reach the Arab Gulf since the uprisings in Tunisia and Egypt.

Just hours before police moved in, the mood in the makeshift tent city was festive and confident.

People sipped tea, ate donated food and smoked apple- and grape-flavored tobacco from water pipes. The men and women mainly sat separately — the women a sea of black in their traditional dress. Some youths wore the red-and-white Bahraini flag as a cape.

After prayers Wednesday evening, a Shiite imam in the square had urged Bahrain's youth not to back down.

"This square is a trust in your hands and so will you whittle away this trust or keep fast?" the imam said. "So be careful and be concerned for your country and remember that the regime will try to rip this country from your hand but if we must leave it in coffins then so be it!"

Across the city, government supporters in a caravan of cars waved national flags and displayed portraits of King Hamad bin Isa Al Khalifa.

"Come join us!" they yelled into markets and along busy streets. "Show your loyalty."

Earlier Wednesday, thousands of mourners turned out for the funeral procession of 31-year-old Fadhel al-Matrook, the second known fatality from the protests. Later, in Pearl Square, his father Salman pleaded with protesters not to give up.

"He is not only my son. He is the son of Bahrain, the son of this nation," he yelled. "His blood shouldn't be wasted."

The bloodshed has brought embarrassing rebukes from allies such as Britain and the United States. A statement from Bahrain's Interior Ministry said suspects have been "placed in custody" in connection with the two protester deaths from earlier in the week, but gave no further details.

The widening challenges to the region's political order — emboldened by the downfall of old-guard regimes in Tunisia and Egypt — also flared elsewhere in Arab world.

In Yemen, the embattled president flooded the ancient capital of Sanaa with more than 2,000 security forces to try to stamp out demonstrations that began nearly a week ago. They turned deadly Wednesday in the southern port of Aden, with two people killed in clashes with police.

In Libya, security forces fired rubber bullets and water cannons at hundreds of marchers in Benghazi, the second-largest city. Witnesses said some police stations were set on fire and one protester said he saw snipers on a roof of a security headquarters firing on protesters.

The unrest was triggered by the temporary detention Tuesday of an activist but quickly turned into a rare public challenge to the 42-year rule of Moammar Gadhafi